固体延焼の基礎的研究(その4) 円管の無炎降下延焼

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As was reported in Part I and Part II, the formula derived theoretically for the downward propagation of smouldering through vertical solid fuels made of paper in various forms such as circular or rectangular rods, and rectangular strips showed a very good coincidence with experimental results. In this report, hollow cylinders of paper were taken as solid fuels and were examined whether or not the same way of thinking was applicable to them.As in the former cases, the dependency of propagation velocity υ upon the inside radius γ of the cylinder was studied. And for the sake of convenience in comparing with the former cases, υ2 was plotted against γ. The results were very different from those of the former cases. With tubes of cardboard 0.9mm thick, for example, υ2 continued to decrease as γ increased from O, and after attaining to its minimum 0.6×l0-4cm2/s2 at γ=1.5mm, υ2 began to increase and attained its maximum of 1.5×l0-4cm2/s2 at about γ=5mm. For further increase of γ, υ2 decreased gradually tending to an asymptotic value of 0.6×l0-4cm2/s2.One of the causes of this complicated relationship was considered to be attributed to the air supply being prevented by the inside wall of the tube, and air was supplied forcibly to its inside. The relation of υ2 - γ was changed remarkably, and υ2 began with 1.7×10-4cm2/s2 (at γ =0) and gradually decreased until at last came to the same asymptotic value of 0.6×10-4cm2/s2υ2 in the region of γ< 0.5 was too large to be explained with the same way of thinking. However, this discrepancy was eliminated by taking into consideration heat radiation from the upper red-heated part to a fire front through the inside space of the cylinder. As a result of this heat radiation, the relation between υ2 and Ta (ambient temperature) was not as simple as were shown in rods. The formula for υ2 in terms of γ, Ta, etc. has been left as a pending problem.
日本火災学会の論文

固体延焼の基礎的研究(その4) 円管の無炎降下延焼

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概要

日本火災学会 | 論文

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